Deep in the textbooks of Reaganomics there is a theory about the split American personality. The theory says that rich Americans behave differently from poor Americans. To be specific, the rich need an incentive to work hard. The poor need a threat. This is the philosophy behind this administration's pet poverty program: compulsory workfare. Since Ronald Reagan came into office, the government has supported a plan that would require able welfare recipients to work or else . . . or else lose their welfare checks.

But while this program is being pushed in Washington, something quite different is happening here in the land of the bean, the cod and Tip O'Neill. There is a workfare program already in place that depends on attracting welfare volunteers. The program, called by the friendly acronym ET (for Employment and Training), is based on the notion that the welfare poor are just like regular people. Give them an incentive and a sensible program, and they'll choose work.

The idea may be radical, but the program is fiscally conservative. It's a perfect match for the image that Mike Dukakis has honed as a governor with a cost-effective social conscience. The program is working, and so are the people.

Under current federal rules, all able welfare recipients -- about half the adults on the rolls -- have to register for a work program. But under ET, what they do next is up to them. They can choose between education, supported work, job placement or none of the above. "The Reagan view is that in a voluntary program there would be no volunteers," says Tom Glynn, deputy commissioner of the Massachusetts Department of Welfare. In fact, however, from a pool of 43,000 registered, a full 25,000 are enrolled in ET, and 13,000 are already in the work force. There is a waiting list to get in ET.

The graduates of ET have saved taxpayers about $22 million so far. They've also helped themselves. On average, the graduates earn $5 an hour or about $10,000 a year, better than the minimum wage. And they stay on the job. After six months, 85 percent are still working, and that's about two or three times more than the average workfare program.

There are two other crucial pieces to the puzzle of this program's popularity: those who go into training get a day-care voucher for a year and keep their Medicaid for 15 months. They are also hired by people who don't know that they're "welfare mothers," so they begin their work lives without a stigma.

Inevitably, the tale of ET has spread, and there have been state delegations sent from as far away as Oregon and Alabama. But the response from Washington has been less than enthusiastic. As Tom Glynn says, "It kills the Reagan people that a liberal Democrat governor in Tip O'Neill's state is running a voluntary ogram that's beating the pants off the punitive workfare in other parts of the country."